1. Field of the Invention
This invention relates to printing presses, and more particularly to high speed printing presses whose blanket cylinder surfaces, printing plates, and mechanisms themselves are all protected against damage on web breaks.
2. Description of the Prior Art
Techniques for stopping a machine which feeds elongated material in the event of breakage of the material are well known. Thus in the patent to Ballard (U.S. Pat. No. 851,214), a lever 70 falls on a paper break to close a stopping circuit. In Veale (U.S. Pat. No. 3,264,740), feelers 58 detect bumps and missing parts to stop the operation of welding apparatus. In Cavanaugh (U.S. Pat. No. 1,776,104), a shoe on arm 32 rides the surface of a web and shuts down the press when paper is absent under the shoe. In Scott (U.S. Pat. No. 2,662,251), a lever 46 falls on a strand break to close a stopping circuit. In Vossen (U.S. Pat. No. 2,747,040), a break in a bobbin thread causes a shift in the needle thread which then displaces lever 52 to close a stop circuit switch. In Howdle et al (U.S. Pat. No. 2,683,195), a plurality of independent shoes 42 each can operate a stop switch in a paper break control device. In Shiba (U.S. Pat. No. 2,896,944) shoes D overlie grooves C on a roll into which they sink on web break. It should be observed that existing detectors essentially do not detect a web break until the break has passed it.